CN117578507A - Method and system for evaluating oscillation stability of direct-driven wind power grid-connected system in fault ride-through period - Google Patents

Method and system for evaluating oscillation stability of direct-driven wind power grid-connected system in fault ride-through period Download PDF

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CN117578507A
CN117578507A CN202311502175.8A CN202311502175A CN117578507A CN 117578507 A CN117578507 A CN 117578507A CN 202311502175 A CN202311502175 A CN 202311502175A CN 117578507 A CN117578507 A CN 117578507A
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fan
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port
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CN117578507B (en
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任必兴
贾勇勇
李强
唐伟佳
吕振华
邹小明
张森
汪成根
李雅然
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State Grid Jiangsu Electric Power Co ltd Innovation And Innovation Center
State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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Abstract

The invention relates to the technical field of wind power generation, in particular to a method and a system for evaluating oscillation stability of a direct-driven wind power grid-connected system in a fault ride-through period, wherein the method comprises the following steps: collecting instantaneous variation of port current, instantaneous variation of port voltage and variation of angular speed output by a phase-locked loop of each fan of the direct-driven wind turbine during fault ride-through; based on the acquired instantaneous value variation, constructing a dynamic energy model of the direct-drive fan network side converter port during fault ride-through; based on the established dynamic energy model, calculating to obtain a dynamic energy negative gradient E of the direct-drive wind power grid-connected system; and on-line evaluation of the stability level of the direct-drive wind power grid-connected system is carried out based on the obtained dynamic energy negative gradient E of the direct-drive wind power grid-connected system. The stability level of the system can be rapidly and effectively evaluated through the magnitude of the inter-machine interaction dynamic energy change rate, the real-time monitoring of the running state of the system is realized, and the efficiency and accuracy of judging the stability of the system are improved.

Description

Method and system for evaluating oscillation stability of direct-driven wind power grid-connected system in fault ride-through period
Technical Field
The invention relates to the technical field of wind power generation, in particular to a method and a system for evaluating oscillation stability of a direct-driven wind power grid-connected system in a fault ride-through period.
Background
With the continuous increase of grid-connected capacity of the direct-driven wind turbine, the stability supporting capacity of wind power to the system is weaker, especially the fault ride-through period is more serious, so that the stability problem of the wind power is gradually brought more and more attention. In recent years, oscillation accidents of a direct-drive wind power grid-connected system frequently occur, and safety and stability problems during system fault ride-through are severely challenged. Therefore, how to evaluate the dynamic stability of the wind farm as a whole during fault ride-through has become a challenge.
At present, the analysis of the oscillation problem of the direct-drive wind power grid-connected system mainly considers the oscillation stability analysis after being disturbed, and the stability problem of the system oscillation during the fault ride-through period is not researched yet. Therefore, analysis of oscillations during a failure of a wind power grid system is a subject that currently requires intensive research.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is known to a person skilled in the art.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: according to the method and the system for evaluating the oscillation stability of the direct-driven wind power grid-connected system in the fault ride-through period, the stability level of the system can be evaluated rapidly and effectively through the magnitude of the inter-machine interaction dynamic energy change rate, the real-time monitoring of the running state of the system is realized, and the efficiency and the accuracy of judging the stability of the system are improved.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a method for evaluating the oscillation stability of a direct-driven wind power grid-connected system in a fault ride-through period comprises the following steps:
collecting instantaneous variation of port current, instantaneous variation of port voltage and variation of angular speed output by a phase-locked loop of each fan of the direct-driven wind turbine during fault ride-through;
based on the acquired instantaneous change of the port current, the acquired instantaneous change of the port voltage and the acquired output angular speed change of the phase-locked loop, constructing a dynamic energy model of the port of the direct-driven fan network-side converter during fault ride-through;
based on the established dynamic energy model, calculating to obtain a dynamic energy negative gradient E of the direct-drive wind power grid-connected system;
and on-line evaluation of the stability level of the direct-drive wind power grid-connected system is carried out based on the obtained dynamic energy negative gradient E of the direct-drive wind power grid-connected system.
Further, the constructing a direct-drive fan network side converter port dynamic energy model during fault ride-through based on the acquired port current instantaneous variable quantity, port voltage instantaneous value variable quantity and phase-locked loop output angular speed variable quantity comprises;
acquiring phase-locked loop dynamic angles and direct-current voltage variation of each fan, current loop current reference value variation and instantaneous value iteration quantity of the port voltage based on acquired port current instantaneous variation, port voltage instantaneous value variation and phase-locked loop output angular speed variation;
and constructing a port dynamic energy model, respectively carrying out iterative computation to obtain disturbance interaction energy, self-coupling interaction energy and inter-machine interaction energy of the direct-drive wind power plant, and calculating to obtain network interaction energy of the direct-drive wind power plant.
Further, the phase-locked loop dynamic angle and the direct current voltage variation of each fan are respectively obtained based on the following formulas, and the instantaneous value iteration quantity of the reference value variation of the current loop current and the port voltage:
△θ pllk (m) ＝-k pθ ∫△u Rqk (m-1) dt-k iθ ∫∫△u Rqk (m-1) dtdt
wherein k is pθ And k iθ The phase-locked loop proportion and integral coefficient are respectively; k (k) p1 And k i1 The proportional and integral coefficients of the fan voltage outer loop are respectively.
Further, the grid-side current transformation of the direct-drive fans during the fault ride-through period of each fan is obtained based on the following formula Port dynamic energy W GSC ：
In the method, in the process of the invention,interactive energy for direct-drive fan grid-side converter, < > for>The energy of the direct-driven fan grid-side converter is provided.
Further, the direct-drive fan network side converter exchanges energyObtained by the formula:
wherein k is pll.p And k pll.i Respectively the proportional and integral coefficients, k, of the phase-locked loop ip_g And k ii_g The current loop ratio and integral coefficient i respectively n.dref And i n.qref Respectively the d-axis current reference value and the q-axis current reference value of the fan, i n.d And i n.q Response currents of d axis and q axis of the fan, delta omega pll The angular velocity variation output by the phase-locked loop.
Further, the direct-drive fan grid-side converter can be self-poweredObtained by the formula:
wherein k is pll.p And k pll.i Respectively the proportional and integral coefficients, k, of the phase-locked loop ip_g And k ii_g The current loop ratio and integral coefficient i respectively n.dref And i n.qref Respectively the d axes of the fansAnd q-axis current reference value, i n.d And i n.q Response currents, omega, of d axis and q axis of fan respectively e To synchronize angular velocity, L T And the filter inductance is used for a fan.
Further, the negative dynamic energy gradient E is the inverse number of the derivative of the dynamic energy of the direct-driven fan grid-side converter port with respect to time, and the expression is as follows:
in which W is GSC And the dynamic energy of the port of the direct-drive fan grid-side converter during fault ride-through.
Further, the stability level is judged by the positive and negative of the dynamic energy negative gradient E, and the judging process is as follows:
When E <0, namely the negative gradient of dynamic energy is negative, the system is in a destabilizing state, and the smaller the value is, the lower the stability level is;
when e=0, the dynamic energy negative gradient is zero, and the system is in a critical stable state;
when E >0, the dynamic energy negative gradient is positive, the system is in steady state, and the larger the value, the higher the stability level.
The invention also provides an oscillation stability evaluation system in the fault ride-through period of the direct-driven wind power grid-connected system, which comprises a data acquisition module, a dynamic energy model construction module, a dynamic energy negative gradient acquisition module, a stability online evaluation module and a result output module;
the data acquisition module is used for acquiring the instantaneous variation of the port current, the instantaneous variation of the port voltage and the variation of the output angular speed of the phase-locked loop of each fan of the direct-driven wind turbine generator during fault ride-through;
the dynamic energy construction module constructs a direct-drive fan network side converter port dynamic energy model in the fault ride-through period based on the acquired port current instantaneous variable quantity, port voltage instantaneous value variable quantity and phase-locked loop output angular speed variable quantity;
the dynamic energy negative gradient acquisition module is used for calculating and acquiring a dynamic energy negative gradient E of the direct-driven wind power grid-connected system based on the established dynamic energy model;
The stability online evaluation module is used for online evaluation of the stability level of the direct-drive wind power grid-connected system based on the obtained dynamic energy negative gradient E of the direct-drive wind power grid-connected system;
and the result output module is used for outputting real-time dynamic energy and stability level of the direct-driven wind power grid-connected system.
Furthermore, the data acquisition module acquires initial oscillation current instantaneous values of the corresponding fan ports through PMU devices arranged on the fan ports, and acquires port current instantaneous variation, port voltage instantaneous value variation and phase-locked loop output angular velocity variation by taking the dominant oscillation mode period as a time interval.
Further, the dynamic energy model construction module comprises an iteration quantity parameter construction unit and a field network interaction energy construction unit;
the iteration quantity parameter construction unit obtains phase-locked loop dynamic angles and direct-current voltage variation of each fan, current loop current reference value variation and instantaneous value iteration quantity of the port voltage based on the acquired port current instantaneous variation, port voltage instantaneous value variation and phase-locked loop output angular speed variation;
the field network interaction energy construction unit is used for constructing a port dynamic energy model, respectively carrying out iterative computation to obtain disturbance interaction energy, self-coupling interaction energy and inter-machine interaction energy of the direct-drive wind power plant, and calculating to obtain the direct-drive wind power plant network interaction energy.
Further, the iteration quantity parameter construction unit obtains the phase-locked loop dynamic angle and the direct-current voltage variation of each fan respectively based on the following formulas:
△θ pllk (m) ＝-k p θ∫△u Rqk (m-1) dt-k i θ∫∫△u Rqk (m-1) dtdt
wherein k is pθ And k iθ The phase-locked loop proportion and integral coefficient are respectively; k (k) p1 And k i1 The proportional and integral coefficients of the fan voltage outer loop are respectively.
Further, the field network interaction energy construction unit obtains dynamic energy W of the direct-drive fan network side converter port during the fault ride-through period of each fan based on the following formula GSC ：
In the method, in the process of the invention,interactive energy for direct-drive fan grid-side converter, < > for>The energy of the direct-driven fan grid-side converter is provided.
Direct-drive fan network side converter interaction energyObtained by the formula:
self energy of direct-drive fan grid-side converterObtained by the formula:
wherein k is pll.p And k pll.i Respectively the proportional and integral coefficients, k, of the phase-locked loop ip_g And k ii_g The current loop ratio and integral coefficient i respectively n.dref And i n.qref Respectively the d-axis current reference value and the q-axis current reference value of the fan, i n.d And i n.q Response currents of d axis and q axis of the fan, delta omega pll For the angular velocity variation, ω, of the phase-locked loop output e To synchronize angular velocity, L T And the filter inductance is used for a fan.
Further, the stability online evaluation module uses a dynamic energy negative gradient E as a discrimination index of system stability, wherein the dynamic energy negative gradient E is the inverse number of the derivative of the dynamic energy of the direct-driven fan network side converter port with respect to time, and the expression is as follows:
In which W is GSC And the dynamic energy of the port of the direct-drive fan grid-side converter during fault ride-through.
Stability level determination with the positive and negative nature of the dynamic energy negative gradient E:
when E <0, namely the negative gradient of dynamic energy is negative, the system is in a destabilizing state, and the smaller the value is, the lower the stability level is;
when e=0, the dynamic energy negative gradient is zero, and the system is in a critical stable state;
when E >0, the dynamic energy negative gradient is positive, the system is in steady state, and the larger the value, the higher the stability level.
The invention also provides electronic equipment, which comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein the processor realizes the steps of the method for evaluating the oscillation stability of the direct-drive wind power grid-connected system during the fault ride-through period when executing the program.
The invention also provides a computer readable storage medium, wherein the storage medium is stored with a computer program, and the computer program realizes the steps of the method for evaluating the oscillation stability of the direct-drive wind power grid-connected system during the fault ride-through period when being executed by a processor.
The beneficial effects of the invention are as follows:
1. the stability level of the grid-connected system of the direct-driven wind power plant during the fault ride-through period is rapidly and effectively evaluated by judging the positive and negative and the magnitude of the dynamic energy negative gradient of the system;
2. The calculation amount is reduced through the dynamic energy construction module, the calculation precision is improved, and the reliable operation of the system is ensured.
3. The system stability level is accurately and quantitatively estimated through the dynamic energy negative gradient index given by the dynamic energy negative gradient acquisition module.
4. And a system stability level judgment result during fault ride-through is given through the stability on-line evaluation module, so that the early warning of the oscillation risk is realized, and the stable and safe operation of the power grid is ensured.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings may be obtained according to the drawings without inventive effort to those skilled in the art.
FIG. 1 is a schematic flow chart of an oscillation stability evaluation method in a fault ride-through period of a direct-driven wind power grid-connected system in an embodiment of the invention;
FIG. 2 is a schematic structural diagram of an oscillation stability evaluation system in a fault ride-through period of a direct-driven wind power grid-connected system in an embodiment of the invention;
FIG. 3 is a schematic structural diagram of a direct-drive wind power grid-connected system in an embodiment of the invention;
FIG. 4 is a graph of the disturbance energy relationship of each fan in scene 1 in a 4-machine wind farm grid-connected system in an embodiment of the invention;
FIG. 5 is a graph of the coupled energy relationship of each fan in scene 1 in a 4-machine wind farm grid-connected system in an embodiment of the invention;
FIG. 6 is a graph of interaction energy of fans in a scene 1 in a 4-machine wind farm grid-connected system in an embodiment of the invention;
FIG. 7 is a graph of interaction energy of a scene 1 grid in a 4-machine wind farm grid-connected system according to an embodiment of the invention;
FIG. 8 is a graph of the disturbance energy relationship of each fan in scene 2 in a 4-machine wind farm grid-connected system in an embodiment of the invention;
FIG. 9 is a graph of the coupled energy relationship of each fan in scene 2 in a 4-machine wind farm grid-connected system in an embodiment of the invention;
FIG. 10 is a graph of interaction energy of fans in a scene 2 in a 4-machine wind farm grid-connected system according to an embodiment of the invention;
FIG. 11 is a graph of interaction energy of a scene 2 grid in a 4-machine wind farm grid-connected system in an embodiment of the invention;
FIG. 12 is a graph of the disturbance energy relationship of each fan in scene 3 in a 4-machine wind farm grid-connected system in an embodiment of the invention;
FIG. 13 is a graph of the coupled energy relationship of each fan in scene 3 in a 4-machine wind farm grid-connected system in an embodiment of the present invention;
FIG. 14 is a graph of interaction energy of fans in scene 3 in a 4-machine wind farm grid-connected system in an embodiment of the invention;
FIG. 15 is a graph of interaction energy of a scene 3 grid in a 4-machine wind farm grid-connected system according to an embodiment of the invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.
It will be understood that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
The method for evaluating the oscillation stability of the direct-drive wind power grid-connected system in the fault ride-through period shown in fig. 1 comprises the following steps:
collecting instantaneous variation of port current, instantaneous variation of port voltage and variation of angular speed output by a phase-locked loop of each fan of the direct-driven wind turbine during fault ride-through;
based on the acquired instantaneous change of the port current, the acquired instantaneous change of the port voltage and the acquired output angular speed change of the phase-locked loop, constructing a dynamic energy model of the port of the direct-driven fan network-side converter during fault ride-through;
based on the established dynamic energy model, calculating to obtain a dynamic energy negative gradient E of the direct-drive wind power grid-connected system;
and on-line evaluation of the stability level of the direct-drive wind power grid-connected system is carried out based on the obtained dynamic energy negative gradient E of the direct-drive wind power grid-connected system.
According to the method, the instantaneous value variation of the initial oscillating current of each wind turbine generator is collected, the instantaneous value variation of the port voltage of each direct-drive fan in the direct-drive wind power plant is collected by taking the period of the dominant oscillating mode as a time interval, the secondary/super-synchronous oscillating stability level of the direct-drive wind power plant is quantitatively estimated on line from the full-time frequency band, and the stability level of the direct-drive wind power plant grid-connected system during fault ride-through is rapidly and effectively estimated by judging the positive and negative and the magnitude of the dynamic energy negative gradient of the direct-drive wind power grid-connected system; the method realizes the real-time monitoring and dynamic tracking of the running state of the direct-drive wind power grid-connected system, and improves the efficiency and accuracy of the stability discrimination of the direct-drive wind power grid-connected system.
Because a plurality of fans exist in the direct-driven wind turbine generator, each fan needs to be monitored and collected in the processing process, so that the instantaneous change of the port current, the instantaneous change of the port voltage and the change of the output angular speed of the phase-locked loop of each fan are obtained, and the port dynamic energy is obtained one by one in the subsequent processing process, so that a dynamic energy model of the port of the direct-driven wind turbine generator network side converter in the fault ride-through period can be constructed, and in the processing process, the data of each fan in the whole direct-driven wind turbine generator system can be comprehensively obtained, monitored and processed, the accuracy of the establishment of the dynamic energy model is ensured, the accuracy of the subsequent stability level assessment is improved, and the accuracy of the oscillation risk early warning is ensured.
On the basis of the embodiment, constructing a dynamic energy model of the port of the direct-drive fan network side converter during fault ride-through based on the acquired port current instantaneous variable quantity, port voltage instantaneous value variable quantity and phase-locked loop output angular speed variable quantity comprises;
acquiring phase-locked loop dynamic angles and direct-current voltage variation of each fan, current loop current reference value variation and instantaneous value iteration quantity of the port voltage based on acquired port current instantaneous variation, port voltage instantaneous value variation and phase-locked loop output angular speed variation;
And constructing a port dynamic energy model, respectively carrying out iterative computation to obtain disturbance interaction energy, self-coupling interaction energy and inter-machine interaction energy of the direct-drive wind power plant, and calculating to obtain network interaction energy of the direct-drive wind power plant.
Firstly, the obtained phase-locked loop dynamic angle, direct current voltage variation, current loop current reference value variation and instantaneous value iteration parameter of the port voltage of each fan provide a basis for the subsequent construction of a port dynamic energy model and also provide a basis for the required variables for the on-line evaluation of the stability level.
Based on the above embodiment, the phase-locked loop dynamic angle and the direct-current voltage variation of each fan are obtained respectively based on the following formulas:
△θ pllk (m) ＝-k pθ ∫△u Rqk (m-1) dt-k iθ ∫∫△u Rqk (m-1) dtdt
wherein k is pθ And k iθ The phase-locked loop proportion and integral coefficient are respectively; k (k) p1 And k i1 The proportional and integral coefficients of the fan voltage outer loop are respectively.
Based on the embodiment, the dynamic energy W of the direct-drive fan network-side converter port during the fault ride-through of each fan is obtained based on the following GSC ：
In the method, in the process of the invention,interactive energy for direct-drive fan grid-side converter, < > for>The energy of the direct-driven fan grid-side converter is provided.
Based on the embodiment, the direct-drive fan network side converter exchanges energy Obtained by the formula:
wherein k is pll.p And k pll.i Respectively the proportional and integral coefficients, k, of the phase-locked loop ip_g And k ii_g The current loop ratio and integral coefficient i respectively n.dref And i n.qref Respectively the d-axis current reference value and the q-axis current reference value of the fan, i n.d And i n.q Response currents of d axis and q axis of the fan, delta omega pll The angular velocity variation output by the phase-locked loop.
Based on the embodiment, the direct-drive fan grid-side converter can self energyObtained by the formula:
wherein k is pll.p And k pll.i Respectively the proportional and integral coefficients, k, of the phase-locked loop ip_g And k ii_g The current loop ratio and integral coefficient i respectively n.dref And i n.qref Respectively the d-axis current reference value and the q-axis current reference value of the fan, i n.d And i n.q Response currents, omega, of d axis and q axis of fan respectively e To synchronize angular velocity, L T And the filter inductance is used for a fan.
Specifically, firstly, a port dynamic energy model is utilized, disturbance interaction energy, self-coupling interaction energy and inter-machine interaction energy of a direct-drive wind power plant are obtained through iterative calculation respectively, and interaction energy of a direct-drive wind power plant network is obtained through calculation:
wherein DeltaW is Farm (m) For the wind power plant dynamic interaction energy of the mth iteration, the disturbance interaction energy delta W Ok (m) Self-coupling interaction energy DeltaW Rk (m) Interaction energy DeltaW between the two computers Ek (m) 3 parts; m is m Rk(n+1) The interaction coefficient between the kth branch and the power grid; m is m Rk Is the spontaneous inductance of the kth branch; Δi Rdk (0) 、△i Rqk (0) Initiating dq-axis instantaneous current variation for the kth branch; deltau Rdk (m) 、△u Rqk (m) 、△u Rdj (m) 、△u Rqj (m) Respectively the m-th dq-axis instantaneous voltage variation of k and j branches; l (L) n+1 Line inductance for ac grid side; l (L) Rk The equivalent inductance of the kth branch is the sum of the inductance of the line of the kth branch and the parallel inductance of other lines inside and outside the wind farm, and meets the following requirementsSimilarly available L Rj 。
Then, setting the total number of wind turbines in the wind farm as n, and obtaining the network interaction energy of the direct-drive wind farm by using the following formula:
by means of constructing the port dynamic energy model, the calculated amount can be effectively reduced, the calculation accuracy is improved, and therefore reliable operation of the system is guaranteed.
Based on the above embodiment, the dynamic energy negative gradient E is the inverse number of the derivative of the dynamic energy of the direct-driven fan grid-side converter port with respect to time, and the expression is:
in which W is GSC And the dynamic energy of the port of the direct-drive fan grid-side converter during fault ride-through.
On the basis of the embodiment, the stability level determination is performed by the positive and negative characteristics of the dynamic energy negative gradient E, and the determination process is as follows:
when E <0, namely the negative gradient of dynamic energy is negative, the system is in a destabilizing state, and the smaller the value is, the lower the stability level is;
When e=0, the dynamic energy negative gradient is zero, and the system is in a critical stable state;
when E >0, the dynamic energy negative gradient is positive, the system is in steady state, and the larger the value, the higher the stability level.
Specifically, when the total number of wind turbines in the wind power plant is n, the obtained interaction energy of the direct-drive wind power plant network is W Farm Then the dynamic energy negative gradient isWhen->When the field network interaction energy change rate is negative, the system is in a stable state, and the smaller the numerical value is, the higher the stability level is; when->When the field network interaction energy change rate is zero, the system is in a critical stable state; when->When the field network interaction energy change rate is positive, the system oscillation divergence is completely unstable.
The stability level of the direct-driven wind power grid-connected system can be accurately and quantitatively estimated by setting the index of the interaction energy change rate of the field network; therefore, a stability level judgment result is given, the early warning of the oscillation risk is realized, and the stable and safe operation of the power grid is ensured.
As shown in FIG. 2, the invention also provides a system for evaluating the oscillation stability of the direct-driven wind power grid-connected system in the fault ride-through period, which comprises a data acquisition module, a dynamic energy model construction module, a dynamic energy negative gradient acquisition module, a stability online evaluation module and a result output module;
The data acquisition module is used for acquiring the instantaneous variation of the port current, the instantaneous variation of the port voltage and the variation of the output angular speed of the phase-locked loop of each fan of the direct-driven wind turbine generator during fault ride-through;
the dynamic energy construction module constructs a direct-drive fan network side converter port dynamic energy model in the fault ride-through period based on the acquired port current instantaneous variable quantity, port voltage instantaneous value variable quantity and phase-locked loop output angular speed variable quantity;
the dynamic energy negative gradient acquisition module calculates and acquires a dynamic energy negative gradient E of the direct-driven wind power grid-connected system based on the established dynamic energy model;
the stability online evaluation module carries out online evaluation on the stability level of the direct-drive wind power grid-connected system based on the obtained dynamic energy negative gradient E of the direct-drive wind power grid-connected system;
the result output module is used for outputting real-time dynamic energy and stability level of the direct-driven wind power grid-connected system.
The dynamic energy model of the direct-drive fan network side converter port during the fault ride-through period can be accurately constructed through the data acquired by the data acquisition module, and the system stability level is accurately quantized and estimated according to the dynamic energy negative gradient index given by the dynamic energy negative gradient acquisition module according to the model; and a system stability level judgment result during fault ride-through is given through the stability on-line evaluation module, so that the early warning of the oscillation risk is realized, and the stable and safe operation of the power grid is ensured.
On the basis of the embodiment, the data acquisition module acquires initial oscillation current instantaneous values corresponding to the fan ports through PMU devices arranged on the fan ports, and acquires port current instantaneous variation, port voltage instantaneous value variation and phase-locked loop output angular velocity variation by taking the dominant oscillation mode period as a time interval.
The system collects the instantaneous value variation of the initial oscillating current of each wind turbine generator set port, and collects the instantaneous value variation of the port voltage of each direct-drive fan in the direct-drive wind power plant by taking the period of the dominant oscillating mode as a time interval, and evaluates the secondary/super-synchronous oscillating stability level of the direct-drive wind power plant in an online quantification mode from the full-time frequency band, so that the real-time monitoring and dynamic tracking of the running state of the system are realized, and the efficiency and accuracy of judging the stability of the system are improved.
On the basis of the embodiment, the dynamic energy model building module comprises an iteration quantity parameter building unit and a field network interaction energy building unit;
the iteration quantity parameter construction unit obtains phase-locked loop dynamic angles and direct-current voltage variation of each fan based on the acquired instantaneous variation of the port current, the acquired instantaneous variation of the port voltage and the acquired instantaneous variation of the phase-locked loop output angular speed, and acquires the current reference value variation of the current loop and the instantaneous iteration quantity of the port voltage;
The field network interaction energy construction unit is used for constructing a port dynamic energy model, respectively carrying out iterative computation to obtain disturbance interaction energy, self-coupling interaction energy and inter-machine interaction energy of the direct-drive wind power plant, and calculating to obtain the direct-drive wind power plant network interaction energy.
On the basis of the above embodiment, the iteration quantity parameter construction unit obtains the phase-locked loop dynamic angle, the direct-current voltage variation of each fan, the current loop current reference value variation and the instantaneous value iteration quantity of the port voltage based on the following formula respectively:
△θ pllk (m) ＝-k p θ∫△u Rqk (m-1) dt-k i θ∫∫△u Rqk (m-1) dtdt
wherein k is pθ And k iθ The phase-locked loop proportion and integral coefficient are respectively; k (k) p1 And k i1 The proportional and integral coefficients of the fan voltage outer loop are respectively.
On the basis of the embodiment, the field network interaction energy construction unit obtains the dynamic energy W of the direct-drive fan network side converter port during the fault ride-through of each fan based on the following GSC ：
In the method, in the process of the invention,interactive energy for direct-drive fan grid-side converter, < > for>The energy of the direct-driven fan grid-side converter is provided.
Direct-drive fan network side converter interaction energyObtained by the formula:
self energy of direct-drive fan grid-side converterObtained by the formula: />
Wherein k is pll.p And k pll.i Respectively the proportional and integral coefficients, k, of the phase-locked loop ip_g And k ii_g The current loop ratio and integral coefficient i respectively n.dref And i n.qref Respectively the d-axis current reference value and the q-axis current reference value of the fan, i n.d And i n.q Response currents of d axis and q axis of the fan, delta omega pll For the angular velocity variation, ω, of the phase-locked loop output e To synchronize angular velocity, L T And the filter inductance is used for a fan.
Specifically, the field network interaction energy construction unit firstly obtains disturbance interaction energy, self-coupling interaction energy and inter-machine interaction energy of the direct-drive wind power plant by using a port dynamic energy model through the following iterative calculation respectively, and calculates to obtain the field network interaction energy of the direct-drive wind power plant:
/>
wherein DeltaW is Farm (m) For the wind power plant dynamic interaction energy of the mth iteration, the disturbance interaction energy delta W Ok (m) Self-coupling interaction energy DeltaW Rk (m) Interaction energy DeltaW between the two computers Ek (m) 3 parts; m is m Rk(n+1) The interaction coefficient between the kth branch and the power grid; m is m Rk Is the spontaneous inductance of the kth branch; Δi Rdk (0) 、△i Rqk (0) Initiating dq-axis instantaneous current variation for the kth branch; deltau Rdk (m) 、△u Rqk (m) 、△u Rdj (m) 、△u Rqj (m) The m-th dq axis instant of k and j branches respectivelyThe amount of time-voltage variation; l (L) n+1 Line inductance for ac grid side; l (L) Rk The equivalent inductance of the kth branch is the sum of the inductance of the line of the kth branch and the parallel inductance of other lines inside and outside the wind farm, and meets the following requirementsSimilarly available L Rj 。
Then, setting the total number of wind turbines in the wind farm as n, and obtaining the network interaction energy of the direct-drive wind farm by using the following formula:
By means of constructing the port dynamic energy model, the calculated amount can be effectively reduced, the calculation accuracy is improved, and therefore reliable operation of the system is guaranteed.
On the basis of the embodiment, the stability online evaluation module uses the dynamic energy negative gradient E as a discrimination index of system stability, wherein the dynamic energy negative gradient E is the inverse number of the derivative of the dynamic energy of the direct-driven fan network side converter port with respect to time, and the expression is as follows:
in which W is GSC And the dynamic energy of the port of the direct-drive fan grid-side converter during fault ride-through.
Stability level determination with the positive and negative nature of the dynamic energy negative gradient E:
when E <0, namely the negative gradient of dynamic energy is negative, the system is in a destabilizing state, and the smaller the value is, the lower the stability level is;
when e=0, the dynamic energy negative gradient is zero, and the system is in a critical stable state;
when E >0, the dynamic energy negative gradient is positive, the system is in steady state, and the larger the value, the higher the stability level.
Specifically, when the total number of wind turbines in the wind power plant is n, the obtained interaction energy of the direct-drive wind power plant network is W Farm Then the dynamic energy negative gradient isWhen->When the field network interaction energy change rate is negative, the system is in a stable state, and the smaller the numerical value is, the higher the stability level is; when- >When the field network interaction energy change rate is zero, the system is in a critical stable state; when->When the field network interaction energy change rate is positive, the system oscillation divergence is completely unstable.
The stability level of the direct-driven wind power grid-connected system can be accurately and quantitatively estimated by setting the index of the interaction energy change rate of the field network; therefore, a stability level judgment result is given, the early warning of the oscillation risk is realized, and the stable and safe operation of the power grid is ensured.
In order to verify the feasibility of the method of the embodiment, a 4-machine wind power plant grid-connected system is built from a simulation layer, different oscillation scenes, namely spontaneous oscillation, forced sub-frequency oscillation and forced super-frequency oscillation, are generated by the system according to different types of disturbance, dynamic energy distribution conditions of the system under three scenes are obtained based on the simulation system, as shown in fig. 3 to 15, by comparing the field network interaction energy change rate obtained by calculation with the embodiment of the invention, the field network interaction energy change rate calculated by the invention meets the precision requirement, and the system stability can be reliably estimated according to the positive and negative and the size of the field network interaction energy change rate.
Specifically, a simulation model is built on an RT-LAB platform; the simulation structure diagram of the direct-drive wind power grid-connected system is shown in fig. 3, and parameters of the direct-drive wind power plant are shown in table 1.
Table 1: main parameters of direct-drive wind farm
/>
When t=4s, setting disturbance on the inner current loops of the fan 1 and the fan 2 to cause spontaneous oscillation of the wind power plant; scene 2 refers to that when t=4s, a 20Hz sub-frequency oscillation source is input at the side of an alternating current power grid, and the sub-frequency forced oscillation of the wind power plant is induced; scene 3 refers to that t=4s is input into an 80Hz over-frequency oscillation source at the side of an alternating current power grid, so that over-frequency forced oscillation of a wind power plant is induced; the disturbance energy, the coupling energy and the interaction energy of the direct-drive wind power plant in different scenes are calculated respectively, time domain waveform diagrams of the energy of each part of the direct-drive wind power plant in scenes 1, 2 and 3 are drawn respectively, and aiming at the time domain waveform diagrams, the energy change condition of the direct-drive wind power plant in different scenes can be analyzed and the influence rules of different influence factors on the stability of the direct-drive wind power plant can be verified.
Fig. 4 to 7 are graphs of the disturbance energy, the coupling energy, the interaction energy and the interaction energy of the field network of each fan in the grid-connected system of the 4-machine wind power field in the scene 1, wherein the disturbance energy, the coupling energy, the interaction energy and the change rate of the direct-driven fans PMSG1 to PMSG4 are positive in the spontaneous oscillation process of the wind power field in the scene 1, and the disturbance energy, the coupling energy and the interaction energy of each device in the wind power field show negative damping characteristics, but the influence on the overall stability level of the wind power field is small and negligible in consideration of the small amplitude of the coupling energy. Because the disturbance energy in the wind power plant is larger than the interaction energy among the devices, the interaction energy of the wind power plant network presents a negative damping characteristic, and the wind power plant externally emits energy. Therefore, in the spontaneous oscillation process of the wind power plant, interaction between the direct-drive fans helps to increase interaction energy of the plant network, and is not beneficial to the stable level of the wind power plant.
FIG. 8 to FIG. 11 are graphs of the relation among disturbance energy, coupling energy, interaction energy and interaction energy of the field network of each fan in the scene 2 in the wind power plant grid-connected system of the machine; in the scene 2, in the process of wind farm subsonic oscillation, disturbance energy and inter-machine interaction energy of the direct-drive fans PMSG1 to PMSG4 and change rate of the disturbance energy and the inter-machine interaction energy are negative, disturbance energy and interaction energy of each device in the wind farm are positive damping characteristics, change rate of coupling energy of each device is positive, the coupling energy is negative damping characteristics, and compared with the disturbance energy, the coupling energy amplitude is smaller and negligible. Because the disturbance energy in the wind power plant is larger than the interaction energy among the devices, the interaction energy of the wind power plant network presents positive damping characteristics, and the wind power plant absorbs energy outwards. Thus, it is demonstrated that interactions between machines during the subsonic oscillations of a wind farm are beneficial for a stable level of the wind farm.
FIG. 12 to FIG. 15 are graphs of the relation among disturbance energy, coupling energy, interaction energy and interaction energy of the field network of each fan in the scene 3 in the wind power plant grid-connected system of the machine; in the scene 3, in the process of over-frequency oscillation of the wind power plant, the energy of each device is opposite to the energy characteristic of each part of the sub-frequency oscillation wind power plant, the interaction energy of the wind power plant network presents a negative damping characteristic, and the wind power plant externally emits energy.
In summary, the direct-drive wind farm dynamic energy model which is established in the embodiment and considers the energy interaction among the devices can reflect different subsynchronous oscillation characteristics of the system, and the proposed stability judgment can reflect the stability level of the system.
The invention also provides an electronic device, which comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein the processor and the memory are connected to a communication bus through a communication interface so as to complete mutual communication, and the processor realizes the step of the method for evaluating the oscillation stability of the direct-drive wind power grid-connected system in the fault ride-through period when executing the program, and comprises the steps of collecting the instantaneous change amount of the port current, the instantaneous change amount of the port voltage and the output angular velocity change amount of a phase-locked loop of each fan of the direct-drive wind power generation set in the fault ride-through period; based on the acquired instantaneous change of the port current, the acquired instantaneous change of the port voltage and the acquired output angular speed change of the phase-locked loop, constructing a dynamic energy model of the port of the direct-driven fan network-side converter during fault ride-through; based on the established dynamic energy model, calculating to obtain a dynamic energy negative gradient E of the direct-drive wind power grid-connected system; based on the obtained dynamic energy negative gradient E of the direct-drive wind power grid-connected system, carrying out on-line evaluation on the stability level of the direct-drive wind power grid-connected system; the stability level of the system can be rapidly and effectively evaluated through the magnitude of the inter-machine interaction dynamic energy change rate, the real-time monitoring of the running state of the system is realized, and the efficiency and accuracy of judging the stability of the system are improved.
The invention also provides a computer readable storage medium which can be sold or used as an independent product, and a computer program is stored on the storage medium, and the computer program realizes the steps of the method for evaluating the oscillation stability of the direct-drive wind power grid-connected system during the fault ride-through period when being executed by a processor; collecting instantaneous variation of port current, instantaneous variation of port voltage and variation of angular speed output by a phase-locked loop of each fan of the direct-driven wind turbine generator during fault ride-through; based on the acquired instantaneous change of the port current, the acquired instantaneous change of the port voltage and the acquired output angular speed change of the phase-locked loop, constructing a dynamic energy model of the port of the direct-driven fan network-side converter during fault ride-through; based on the established dynamic energy model, calculating to obtain a dynamic energy negative gradient E of the direct-drive wind power grid-connected system; based on the obtained dynamic energy negative gradient E of the direct-drive wind power grid-connected system, carrying out on-line evaluation on the stability level of the direct-drive wind power grid-connected system; the stability level of the system can be rapidly and effectively evaluated through the magnitude of the inter-machine interaction dynamic energy change rate, the real-time monitoring of the running state of the system is realized, and the efficiency and accuracy of judging the stability of the system are improved.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The solutions in the embodiments of the present application may be implemented in various computer languages, for example, object-oriented programming language Java, and an transliterated scripting language JavaScript, etc.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the application.
It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (16)

1. The method for evaluating the oscillation stability of the direct-driven wind power grid-connected system in the fault ride-through period is characterized by comprising the following steps of:
collecting instantaneous variation of port current, instantaneous variation of port voltage and variation of angular speed output by a phase-locked loop of each fan of the direct-driven wind turbine during fault ride-through;
based on the acquired instantaneous change of the port current, the acquired instantaneous change of the port voltage and the acquired output angular speed change of the phase-locked loop, constructing a dynamic energy model of the port of the direct-driven fan network-side converter during fault ride-through;
based on the established dynamic energy model, calculating to obtain a dynamic energy negative gradient E of the direct-drive wind power grid-connected system;
and on-line evaluation of the stability level of the direct-drive wind power grid-connected system is carried out based on the obtained dynamic energy negative gradient E of the direct-drive wind power grid-connected system.
2. The method for evaluating the oscillation stability of the direct-driven wind power grid-connected system in the fault ride-through period according to claim 1, wherein the constructing the dynamic energy model of the direct-driven fan grid-side converter port in the fault ride-through period based on the acquired instantaneous change of the port current, the instantaneous change of the port voltage and the change of the output angular velocity of the phase-locked loop comprises the following steps of;
acquiring phase-locked loop dynamic angles and direct-current voltage variation of each fan, current loop current reference value variation and instantaneous value iteration quantity of the port voltage based on acquired port current instantaneous variation, port voltage instantaneous value variation and phase-locked loop output angular speed variation;
and constructing a port dynamic energy model, respectively carrying out iterative computation to obtain disturbance interaction energy, self-coupling interaction energy and inter-machine interaction energy of the direct-drive wind power plant, and calculating to obtain network interaction energy of the direct-drive wind power plant.
3. The method for evaluating the oscillation stability of the direct-drive wind power grid-connected system in the fault ride-through period according to claim 2, wherein the phase-locked loop dynamic angle and the direct-current voltage variation of each fan, the current loop current reference value variation and the instantaneous value iteration quantity of the port voltage are respectively obtained based on the following steps:
△θ pllk (m) ＝-k pθ ∫△u Rqk (m-1) dt-k iθ ∫∫△u Rqk (m-1) dtdt
Wherein k is pθ And k iθ The phase-locked loop proportion and integral coefficient are respectively; k (k) p1 And k i1 The proportional and integral coefficients of the fan voltage outer loop are respectively.
4. The method for evaluating the oscillation stability of a direct-drive wind power grid-connected system during fault ride-through according to claim 3, wherein the fault of each fan is obtained based on the following formulaDynamic energy W of port of grid-side converter of direct-drive fan during crossing GSC ：
In the method, in the process of the invention,interactive energy for direct-drive fan grid-side converter, < > for>The energy of the direct-driven fan grid-side converter is provided.
5. The method for evaluating the oscillation stability of a direct-drive wind power grid-connected system in a fault ride through period according to claim 4, wherein the direct-drive fan grid-side converter is capable of interacting energyObtained by the formula:
wherein k is pll.p And k pll.i Respectively the proportional and integral coefficients, k, of the phase-locked loop ip_g And k ii_g The current loop ratio and integral coefficient i respectively n.dref And i n.qref Respectively the d-axis current reference value and the q-axis current reference value of the fan, i n.d And i n.q Response currents of d axis and q axis of the fan, delta omega pll The angular velocity variation output by the phase-locked loop.
6. The method for evaluating the oscillation stability of the direct-driven wind power grid-connected system in the fault ride through period according to claim 5, wherein the direct-driven fan grid-side converter is self-energy Obtained by the formula:
wherein k is pll.p And k pll.i Respectively the proportional and integral coefficients, k, of the phase-locked loop ip_g And k ii_g The current loop ratio and integral coefficient i respectively n.dref And i n.qref Respectively the d-axis current reference value and the q-axis current reference value of the fan, i n.d And i n.q Response currents, omega, of d axis and q axis of fan respectively e To synchronize angular velocity, L T And the filter inductance is used for a fan.
7. The method for evaluating the oscillation stability of the direct-driven wind power grid-connected system in the fault ride through period according to claim 1, wherein the negative dynamic energy gradient E is the inverse number of the derivative of the dynamic energy of the direct-driven fan grid-side converter port with respect to time, and the expression is as follows:
in which W is GSC And the dynamic energy of the port of the direct-drive fan grid-side converter during fault ride-through.
8. The method for evaluating the oscillation stability of the direct-driven wind power grid-connected system in the fault ride through period according to claim 7, wherein the stability level judgment is carried out by the positive and negative polarities of a dynamic energy negative gradient E, and the judgment process is as follows:
when E <0, namely the negative gradient of dynamic energy is negative, the system is in a destabilizing state, and the smaller the value is, the lower the stability level is;
when e=0, the dynamic energy negative gradient is zero, and the system is in a critical stable state;
when E >0, the dynamic energy negative gradient is positive, the system is in steady state, and the larger the value, the higher the stability level.
9. The system is characterized by comprising a data acquisition module, a dynamic energy model construction module, a dynamic energy negative gradient acquisition module, a stability online evaluation module and a result output module;
the data acquisition module is used for acquiring the instantaneous variation of the port current, the instantaneous variation of the port voltage and the variation of the output angular speed of the phase-locked loop of each fan of the direct-driven wind turbine generator during fault ride-through;
the dynamic energy construction module constructs a direct-drive fan network side converter port dynamic energy model in the fault ride-through period based on the acquired port current instantaneous variable quantity, port voltage instantaneous value variable quantity and phase-locked loop output angular speed variable quantity;
the dynamic energy negative gradient acquisition module is used for calculating and acquiring a dynamic energy negative gradient E of the direct-driven wind power grid-connected system based on the established dynamic energy model;
the stability online evaluation module is used for online evaluation of the stability level of the direct-drive wind power grid-connected system based on the obtained dynamic energy negative gradient E of the direct-drive wind power grid-connected system;
and the result output module is used for outputting real-time dynamic energy and stability level of the direct-driven wind power grid-connected system.
10. The system for evaluating the oscillation stability of the direct-driven wind power grid-connected system during the fault ride-through period according to claim 9, wherein the data acquisition module acquires an initial oscillation current instantaneous value corresponding to a fan port through a PMU device arranged on each fan port, and acquires a port current instantaneous change, a port voltage instantaneous value change and a phase-locked loop output angular velocity change at a time interval of a dominant oscillation mode period.
11. The system for evaluating the oscillation stability of the direct-driven wind power grid-connected system in the fault ride-through period according to claim 9, wherein the dynamic energy model building module comprises an iteration quantity parameter building unit and a field network interaction energy building unit;
the iteration quantity parameter construction unit obtains phase-locked loop dynamic angles and direct-current voltage variation of each fan, current loop current reference value variation and instantaneous value iteration quantity of the port voltage based on the acquired port current instantaneous variation, port voltage instantaneous value variation and phase-locked loop output angular speed variation;
the field network interaction energy construction unit is used for constructing a port dynamic energy model, respectively carrying out iterative computation to obtain disturbance interaction energy, self-coupling interaction energy and inter-machine interaction energy of the direct-drive wind power plant, and calculating to obtain the direct-drive wind power plant network interaction energy.
12. The system for evaluating the oscillation stability of the direct-driven wind power grid-connected system during the fault ride-through period according to claim 11, wherein the iteration quantity parameter construction unit is used for respectively obtaining the phase-locked loop dynamic angle and the direct-current voltage variation of each fan, the current loop current reference value variation and the instantaneous value iteration quantity of the port voltage based on the following steps:
△θ pllk (m) ＝-k pθ ∫△u Rqk (m-1) dt-k iθ ∫∫△u Rqk (m-1) dtdt
wherein k is pθ And k iθ The phase-locked loop proportion and integral coefficient are respectively; k (k) p1 And k i1 The proportional and integral coefficients of the fan voltage outer loop are respectively.
13. The system for evaluating the oscillation stability of a direct-drive wind power grid-connected system during fault ride-through according to claim 12, wherein the field network interaction energy construction unit obtains the dynamic energy W of the direct-drive fan network-side converter port during the fault ride-through of each fan based on the following formula GSC ：
In the method, in the process of the invention,interactive energy for direct-drive fan grid-side converter, < > for>The energy of the direct-driven fan grid-side converter is provided.
Direct-drive fan network side converter interaction energyObtained by the formula:
self energy of direct-drive fan grid-side converterObtained by the formula:
wherein k is pll.p And k pll.i Respectively phase-locked loop ratiosExample and integral coefficient, k ip_g And k ii_g The current loop ratio and integral coefficient i respectively n.dref And i n.qref Respectively the d-axis current reference value and the q-axis current reference value of the fan, i n.d And i n.q Response currents of d axis and q axis of the fan, delta omega pll For the angular velocity variation, ω, of the phase-locked loop output e To synchronize angular velocity, L T And the filter inductance is used for a fan.
14. The system for evaluating the oscillation stability of the direct-driven wind power grid-connected system in the fault ride through period according to claim 9, wherein the stability online evaluation module uses a dynamic energy negative gradient E as a discrimination indicator of system stability, the dynamic energy negative gradient E is an inverse number of a derivative of dynamic energy of a port of a direct-driven fan grid-side converter with respect to time, and the expression is as follows:
in which W is GSC And the dynamic energy of the port of the direct-drive fan grid-side converter during fault ride-through.
Stability level determination with the positive and negative nature of the dynamic energy negative gradient E:
when E <0, namely the negative gradient of dynamic energy is negative, the system is in a destabilizing state, and the smaller the value is, the lower the stability level is;
when e=0, the dynamic energy negative gradient is zero, and the system is in a critical stable state;
when E >0, the dynamic energy negative gradient is positive, the system is in steady state, and the larger the value, the higher the stability level.
15. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor, when executing the program, implements the steps of the method for evaluating the oscillation stability during the fault ride-through period of the direct drive wind power grid-connected system according to any one of claims 1 to 8.
16. A computer-readable storage medium, wherein a computer program is stored on the storage medium, and the computer program realizes the steps of the method for evaluating the oscillation stability of the direct-drive wind power grid-connected system during the fault ride-through period according to any one of claims 1 to 8 when the computer program is executed by a processor.
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